When copper tarnishes and then becomes clear again this is because the top layer of the copper has dissolved as aqeous Cu(II) ions. You're correct in saying that copper is an essential element but as Paracelsus used to say, it's all about the concentration. The amount of copper the wort comes into contact with is much larger in homebrewing then in professional brewing because they work with much much larger volumes, which makes for a much more sensible wort volume to copper surface area ratio.

The simple fact is that a daily intake of 10mg is plenty and that food serves easily in this demand. The fact that your stepmom doesn't show any of the symptoms (not blue retinas but yellow rings around them btw, I made a mistake) is because she has a copper deficiency. Copper surplus in the body is hard to relieve just like other heavy metal poisoning is. The simple fact of the matter being that heavy metals collect in the body and usually have a hard time leaving it. They are to be handled with a certain degree of caution, lead is not the only toxic metal (copper poisoning is a lot like arsenic poisoning for instance!).

The effect may take many years to reveal itself but once it does you're screwed! Be careful! If the cooler is covered in that ugly layer just rinse it in citric acid solution to make it nice and clear and quickly rinse it. It'll be nice and shiny and clear of soluble copper. It may seem like a stretch now but it's going to pay off in the long run.

Reason: Personal attack removed by Yooperbrew and addition to post by Nerro

When copper tarnishes and then becomes clear again this is because the top layer of the copper has dissolved as aqeous Cu(II) ions. You're correct in saying that copper is an essential element but as Paracelsus used to say, it's all about the concentration. The amount of copper the wort comes into contact with is much larger in homebrewing then in professional brewing because they work with much much larger volumes, which makes for a much more sensible wort volume to copper surface area ratio.

The simple fact is that a daily intake of 10mg is plenty and that food serves easily in this demand. The fact that your stepmom doesn't show any of the symptoms (not blue retinas but yellow rings around them btw, I made a mistake) is because she has a copper deficiency. Copper surplus in the body is hard to relieve just like other heavy metal poisoning is. The simple fact of the matter being that heavy metals collect in the body and usually have a hard time leaving it. They are to be handled with a certain degree of caution, lead is not the only toxic metal (copper poisoning is a lot like arsenic poisoning for instance!).

The effect may take many years to reveal itself but once it does you're screwed! Be careful! If the cooler is covered in that ugly layer just rinse it in citric acid solution to make it nice and clear and quickly rinse it. It'll be nice and shiny and clear of soluble copper. It may seem like a stretch now but it's going to pay off in the long run.

Wouldn't we all be insane by now? Don't they use copper in breweries. Didn't breweries use to (some still do) boil in copper kettles?

At the beginning of my brewing process, I take my chiller and put it in a bucket of oxyclean. By the time it is needed in my wort, almost all the dark film is off the coils. I just spray it down with a hose real good and put it in the wort.

I agree with Nerro copper is toxic. Breweries do use copper, but it is clean copper. If your chiller is clean and shinny going in and coming out the amounts of copper added to your wort should be at a safe level. If your chiller is dull and oxidized and comes out shiny you have left that copper oxide in your wort. Keep your copper clean.

EvilTOJ's mother-in-law appears to have Wilson's disease, which is a hereditary disease of copper storage resulting in accumulation of copper, leading to the rings of copper deposits in the cornea (not retina) and leading more seriously to cirrhosis of the liver (unrelated to excessive alcohol intake).

Nerro, you may want to check your facts. It is possible to have copper toxicity in the absence of the genetic defect of Wilson's disease, but that is most likely to happen in Indian children with another genetic defect. It is pretty unlikely unless you have these defects, or unless you consume gram quantities of copper salts, like copper sulfate. If you can drink beer with that much copper in it you are a better man than I. It is hard to imagine that being very tasty. If you did, you would get gastrointestinal symptoms first, like nausea, vomiting, and diarrhea.

In 20+ years of practicing internal medicine I have never seen or heard of a case of copper toxicity. I won't lose sleep over the copper in my counterflow chiller.

Unless it is really poorly stored your chiller probably only has copper oxides on it. If you are leaching away these copper oxides the tubing should get thinner and eventually perforate. If that does not happen, then the wort is reducing the copper oxides back to metallic copper. That reaction would release a little oxygen into the wort, but not copper, as I recall my chemistry (It has been a lot of years).

For you guys who don't use something like Oxyclean on your chiller, does the copper tubing thin out over time?

On a sidenote, I considered the possibility of the wort reducing the CuO and Cu2O back to copper and water (never oxygen). This might be possible in the presence of reducing sugars like glucose and such. However those sugars only really reduce metal oxides in alkaline environments, wort is somewhat acidic and as such it is much more likely that the oxides simply go through some proton exchange to yield aqeous copper ions and water.